Ab Initio Molecular Cluster Calculation

    At UCLA, we have developed a method of simulating reactions on compound semiconductor surfaces using molecular cluster calculations with density functional theory.  Shown below is a cluster model of the gallium arsenide surface.  This cluster represents all the reaction sites on the surface, i.e., an arsenic dimer and two second-layer gallium atoms.  On the optimized cluster, each arsenic dangling bond is filled with a pair of electrons, while each gallium dangling bond is empty.  This is in excellent agreement with the experimental observations.  The most exciting result from this work is that we can predict the vibrational frequencies of the optimized clusters and compare these results with our infrared data.  This unique capability allows us to definitely assign the observed vibrational bands to specific adsorption sites.  Furthermore, I have extended this method to study the reaction mechanisms of organometallic precursors on the semiconductor surfaces. 

More on molecular clusters:

1. Decomposition mechanism of arsine on GaAs (001)-(4x2)
2. InP (001)-(2x1) and its spin density distribution
3. Hydrogen adsorption on InP (001)-(2x1)
4. Hydrogen adsorption on InP (001)-(2x4)